<nav class="navbar navbar-light bg-faded">
  <a class="navbar-brand" href="#">Learning Bootstrap 4</a>
  <ul class="nav navbar-nav">
    <li class="nav-item active">
      <a class="nav-link" href="index.html">Home</a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="about.html">About</a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="contact.html">Contact</a>
    </li>
  </ul>
  <form class="form-inline pull-xs-right">
    <input class="form-control" type="text" placeholder="Search">
    <button class="btn btn-primary" type="submit">Search</button>
  </form>
</nav>